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<div><a href="../index.html">Home</a> &gt;  <a href="index.html">utilities</a> &gt; isintriangle.m</div>

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<h1>isintriangle
</h1>

<h2><a name="_name"></a>PURPOSE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="box"><strong>determine if point (x0,y0) is in triangle defined by nodes (xt(3),yt(3))</strong></div>

<h2><a name="_synopsis"></a>SYNOPSIS <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="box"><strong>function res = isintriangle(xt,yt,x0,y0) </strong></div>

<h2><a name="_description"></a>DESCRIPTION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="fragment"><pre class="comment">  determine if point (x0,y0) is in triangle defined by nodes (xt(3),yt(3))    

  function res = isintriangle(xt,yt,x0,y0)

  determine if point (x0,y0) is in triangle defined by nodes (xt(3),yt(3))    |
  using algorithm used for scene rendering in computer graphics               |
  algorithm works well unless particle happens to lie in a line parallel      |
  to the edge of a triangle.                                                  |
  This can cause problems if you use a regular grid, say for idealized        |
  modelling and you happen to seed particles right on edges or parallel to    |
  edges.                                                                      |
==============================================================================|</pre></div>

<!-- crossreference -->
<h2><a name="_cross"></a>CROSS-REFERENCE INFORMATION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
This function calls:
<ul style="list-style-image:url(../matlabicon.gif)">
</ul>
This function is called by:
<ul style="list-style-image:url(../matlabicon.gif)">
<li><a href="inkmlbb.html" class="code" title="function [pts] = inkmlbb(fname,x,y)">inkmlbb</a>	fname = 'Wet_Skagit_BB.kml';</li></ul>
<!-- crossreference -->



<h2><a name="_source"></a>SOURCE CODE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>
<div class="fragment"><pre>0001 <a name="_sub0" href="#_subfunctions" class="code">function res = isintriangle(xt,yt,x0,y0)</a>
0002 <span class="comment">%  determine if point (x0,y0) is in triangle defined by nodes (xt(3),yt(3))</span>
0003 <span class="comment">%</span>
0004 <span class="comment">%  function res = isintriangle(xt,yt,x0,y0)</span>
0005 <span class="comment">%</span>
0006 <span class="comment">%  determine if point (x0,y0) is in triangle defined by nodes (xt(3),yt(3))    |</span>
0007 <span class="comment">%  using algorithm used for scene rendering in computer graphics               |</span>
0008 <span class="comment">%  algorithm works well unless particle happens to lie in a line parallel      |</span>
0009 <span class="comment">%  to the edge of a triangle.                                                  |</span>
0010 <span class="comment">%  This can cause problems if you use a regular grid, say for idealized        |</span>
0011 <span class="comment">%  modelling and you happen to seed particles right on edges or parallel to    |</span>
0012 <span class="comment">%  edges.                                                                      |</span>
0013 <span class="comment">%==============================================================================|</span>
0014 
0015  res = 0;
0016  f1 = (y0-yt(1))*(xt(2)-xt(1)) - (x0-xt(1))*(yt(2)-yt(1));
0017  f2 = (y0-yt(3))*(xt(1)-xt(3)) - (x0-xt(3))*(yt(1)-yt(3));
0018  f3 = (y0-yt(2))*(xt(3)-xt(2)) - (x0-xt(2))*(yt(3)-yt(2));
0019  <span class="keyword">if</span>(f1*f3 &gt;= 0.0 &amp; f3*f2 &gt;= 0.0) 
0020    res = 1;
0021  <span class="keyword">end</span>;
0022 
0023  <span class="keyword">return</span>
0024</pre></div>
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